<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=<sr>, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // alert("Hello World")
        // var name = "zhangsan";
        // var age = 20;

        // var a = 10;//数字
        // a = "haha";//字符串

        // var a = 10;
        // console.log(typeof a);//number

        // var b = "hello";
        // console.log(typeof b);//string

        // var c = true;
        // console.log(typeof c);//boolean

        // var d;
        // console.log(typeof d);//undefined

        // var e = null;
        // console.log(typeof e);//null

        var age = 20;//number
        var age1 = "20";//string
        var age2 = 20;//number

        console.log(age == age1);//true，会进行隐式转换,比较的是值，值是一样的
        console.log(age === age1);//false，不会进行隐式转换，类型不一样
        console.log(age == age2);//true，类型和值都一样
    </script>
</body>
</html>